Damaged ECU - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 04-09-2009, 07:55 AM Thread Starter
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Date registered: Apr 2009
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Damaged ECU

Wonder if anyone would comment on the following regarding a repair and subsequent damage to a ECU, are my comments valid and is the garages comments valid?

Inital Garages comments Black
My Comments: Blue
Garage Reply: RED

Car came into garage with a complaint of a fuel smell; Vehicle assesed and fault found was the fuel injectors leaking at the point where they seat in the cylinder head. This causes compression, exhaust fumes and unburnt fuel to 'chuff' into space under bonnet. The rectification is to remove injectors, clean holes, replace sealing rings and refit injectors. This was done and car returned to yourself.

Were any replacement injectors fitted at this point? Were new fixing clamp bolts used when re-fitting or were the existing bolts re-fitted? If new injector/s were fitted were they / these coded to the ECU- If so how were these coded i.e. what equipment was used to re-code the ECU?

No replacement injectors fitted at this stage, it was only the sealing rings at fault.

Following day Nicky called to say smell of fuel was worse than before after driving a few miles. The vehicle was returned to workshop and assesed. Number 1 injector had been pushed up from its seat so asll the fuel and all the compression from this cylinder was leaking into engine compartment. This was due to when fitting the securing bolt that holds the injector tight to the cylinder head was tightened it stripped the thread so the injector could not hold down tight. This was missed on reassembly and come adrift after driving just a few miles.

Nikki called to say the car was running like a chug boat and totally un-driveable with steam coming from under the bonnet, with the car sounding like it’s going to explode

Correct this was due to the explanation above.

We removed the injector, fitted a sleeve into cylinder head to give injector a good thread to tighten to. The cam cover, injector, bolt and pipe were replaced along with plastic covers over the engine that had been damaged, the dent to bonnet was caused when this injector came adrift and repairs are planned for this at a bodyshop at a later date as agreed with Nicky.

I assume that the injector that damage the bonnet was replaced at this point? If so, Once again were new fixing clamp bolts used when re-fitting and were the injectors coded to the ECU if so how?

Yes, injector, clamp and bolt were replaced at this point.

With this repair each individual fuel pipe from common rail to each injector to be replaced, was this done?

With the replacement injector a new pipe was fitted.

As each injector is wired, is it not feasible this wire was stretched when lifting occurred due to the failed bolt causing a short, which potentially could cause damage to the ECU??

No the wires are well insulated, there is slack within the loom to allow for movement and the ecu fault relates to no 2 and no 5 fueling circuit, this is why a fault of injector was diagnosed twice at no 2

Fault could also be in wiring harness where damaged occurred, was this checked?

All looms were tested by ourselves and by mercedes.

The car was returned to yourself. After driving into work you reported a lack of power. We again took the car back into workshop and spent many many man hours checking and testing to try to find cause of this lack of power.

We came up with no cureing solution so decided to take the car to the mercedes specialist in Cambridge to see if we were missing anything.
They advised a fault on another injector (number 2) this was replaces and the system all reset to the new injectors.

The car was returned to yourself. Nicky drove to stables and all seemed fine. On way home a warning light came on and lack of power followed.
I came to your home and carried out some diagnostic checks which revealed a fault with the air mass meter which measures the amount of air being drawn into engine and adjusts fuel quantity as required. The checks also revealed a faulty glow plug relay, ths controls the pre heating plugs in the engine which work when the orange coil light comes on pre starting to warm the air inside engine to aid starting, This fault would not cause any lack of power. We again took the car back to workshop and replaces both parts. These faults are not connected with the injector removal and replacement but I felt that I should replace for you free of charge. This put the warning light out but we still had a lack of power.

Lots more man hours followed to find a solution including help from our technical 'bods' It was agreed to remove the inlet manifold to check on the air flaps. These flaps inside the manifold are moved electronically to vary the air entering the cylinder at different engine loads.

We found that on number 2 cylinder this flap had a broken linkage and was jammed shut. Finally we thought we had found the problem. Two days labour and a new linkage later we still had a lack of power, again this fault with the flap is unrelated to the work carried out on the injectors.

More man hours crying over your engine were spent by grown men! We drew blanks so decided to get another opinion from Mercedes in Cambridge.

The car was sent into the dealer and after a couple of days they reported back with a faulty no 2 injector. Now this had been replaced already.

The following day they reported back to say replacing the injector did not cure the fault and they refitted the one they took out.

3 days later they reported back with suspected fault within the main brain of the car and a test unit had been requested from Germany.

The dealer requested authority to replace unit an a cost of about £1000.00 to cure the fault. Again this fault has no relation to injector work carried out during the first visit to Mitchell's

We have spent many many hours to try to resolve this, fitted failed parts on the way at no cost but cannot continue to pay for any more repairs that arrise on the car. All of our work carrys a warranty for faulty workmanship and all of the parts we fit have a 12 month warranty. This was put to the test and passed with the repairs carried out when injector bolt thread failed.

How can you be sure that the ECU was not damage at the point in time of the injector lifting?

I can be sure of this as the ecu fault relates to different cylinder circuits as explained above, as with the manifold flap, glow relay and air mass all these faults are coincidental to follow after repair of leaking injector seals.
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post #2 of 3 (permalink) Old 04-11-2009, 01:10 PM
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nick - Very interesting.

It would help if you could use the UserCP ^^^ and add some details about your model/location, etc. At the moment all we know it that you have a diesel, and are located near Cambridge (UK?)
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post #3 of 3 (permalink) Old 04-11-2009, 01:38 PM
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I guess I don't quite understand your question: what do you mean by "valid"? Are you suggesting they're lying to you?

Felicita e un bicchiere di vino con un panino.
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